Ion implanters are conventionally utilized to place a specified quantity of dopants or impurities within semiconductor workpieces or wafers. In a typical ion implantation system, a dopant material is ionized, therein generating a beam of ions. The ion beam is directed at a surface of the semiconductor wafer to implant ions into the wafer, wherein the ions penetrate the surface of the wafer and form regions of desired conductivity therein. For example, ion implantation has particular use in the fabrication of transistors in semiconductor workpieces. A typical ion implanter comprises an ion source for generating the ion beam, a beamline assembly having a mass analysis apparatus for directing and/or filtering (e.g., mass resolving) ions within the beam, and a target chamber containing one or more wafers or workpieces to be treated.
Various types of ion implanters allow respectively varied dosages and energies of ions to be implanted, based on the desired characteristics to be achieved within the workpiece. For example, high-current ion implanters are typically used for high dose implants, and medium-current to low-current ion implanters are utilized for lower dose applications. An energy of the ions can further vary, wherein the energy generally determines the depth to which the ions are implanted within the workpiece, such as to control junction depths in semiconductor devices. Typically, low- to medium-current implanters have a substantial length of travel of the ion beam (also called the beamline of the implanter) before it impacts the workpiece. High-current implanters, however, typically have a much shorter beamline due, at least in part, to the low energies associated with the ion beam, wherein the high-current ion beams tend to lose coherence with longer beamlines.
As device geometries continue to shrink, shallow junction contact regions translate into requirements for lower and lower energies of the ion beam. Additionally, requirements for precise dopant placement have resulted in ever-more demanding requirements for minimizing beam angle variation, both within the beam, and across the substrate surface. For example, in certain applications, implants at energies down to 300 electron Volts are desirable, while concurrently minimizing energy contamination, maintaining tight control of angle variation within the ion beam as well as across the workpiece, and also while providing high workpiece processing throughput.
At present, several architectures exist to achieve low energies, however, these architectures typically utilize magnets to parallelize the ion beam after mass resolution. The presence and required configuration of the magnets, however, tends to provide a beamline that is longer than desirable, thus needing higher beam currents or energies to simply transport the ion beam through the apparatus. Accordingly, it can be appreciated that an improved beamline architecture is desirable for providing both a low dose implant with a minimal beamline length.